Текст 9

Mobile phones

In the early 1870s, Alexander Graham Bell invented a way for an electric wire to carry a human voice. In the 1876, he made the first telephone. In the 1880s and 1890s, many scientists worked to invent a way to send a signal without using wires. In 1896, Guglielmo Marconi made the first radio transmission. He sent a radio signal from Wales to England. Soon, both telephones and radios were popular ways of communication.

Now all of us are using mobile phones. A mobile telephone is basically a small radio. A radio uses electricity to send a person’s voice over a long distance to another radio. It doesn’t use wires. A voice that is sent by a radio is called a signal.

A radio signal travels very quickly. Only a few years ago, mobile telephones were very large. They needed large batteries. They had to be powerful to send their signal over long distances. This was because most cities had only one antenna tower for mobile phones.

Today’s mobile phones are small and easy to use. Nowadays, most cities have a lot of antenna towers, not just one. This means that each mobile phone only has to send a signal a short distance, so they don’t need to be so powerful. Mobile phones today use small batteries. A large city, where lots of mobile phones are used, can have hundreds of towers. (after Lewis Lansford and D’Arcy Adrian Vallance, Comprehension 2)

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